…So, did we make things better, or worse?
Oh, better. I already knew I was pissy! 
I feel awkward now.
I’m betting you’re joking, but if not WE definitely are. We were just wondering how people tended to define that particular bit of slang.
Now, if we were talking about “pissed,” that gets more complicated. “I was so pissed because my husband got pissed at the company party and pissed on the potted plants.”
(Yes, joke. All good. )
I’d take it to mean that his cat’s pregnant.
That he’s in a grouchy mood, but not overwhelmingly so.
“Pissy” is temporary and kind of silly to observers, an adult tantrum. To the extent it’s taken out on the world, the world kind of stares in amusement.
The angry snack food:
Pissed Stachios
Without looking at other responses: he’s in a grouchy mood, easily pissed off, and ready to take offense at the slightest thing.
With facial hair!
Not so fast there mister … you got some ‘splainin’ to do. 
Irritating, irritated, unpleasant to be around.
I ain’t got nuthin’ to 'splain! It ain’t my thread. 
pissy, crabby, cross, grouchy, irritable, bitchy, grumpy, dopey, and doc
I would equate it with “cranky,” rather than mad. Someone who is prone just to go off, but not really get mad.
I agree with everyone else: it means cranky, irritable.
Unless the person who said it has a lisp. Then it might mean terse, not given to excessive verbiage.
Grouchy mood, also referred to as having a case of the red ass.
I’d say it’s basically “pissed off”, but in general rather than about something specific.